Catheter and Method for Improved Irrigation

ABSTRACT

Various catheters with expandable and contractible fluid pathways extending therethrough, and methods of use, are provided herein. In an exemplary embodiment, a catheter is provided with an elongate body having an electrode at the distal end thereof. One or more expandable members or wings can extend between the electrode and the distal end of the elongate body. The catheter can also include an actuator extending therethrough and coupled to the electrode such that movement of the actuator is effective to advance and retract the electrode, thereby moving the one or more expandable members between a collapsed configuration and an expanded configuration. The catheter can also include a fluid sealed lumen formed therein and configured to receive fluid and to deliver fluid to one or more pathways formed in the electrode. The actuator can extend through the fluid sealed lumen, however it can be fluidly separated from the lumen. The fluid sealed lumen can be configured to expand and collapse with movement of the electrode, while allowing movement of the actuator therethrough.

This application claims priority from U.S. Provisional App. No.62/562,934, filed Sep. 25, 2017, which is incorporated herein in itsentirety.

FIELD

Catheters, and in particular irrigated ablation catheters, are provided,as well as methods for using the same.

BACKGROUND

A variety of operations require the use of a catheter to deliverirrigation to a surgical site. For example, treatment of cardiacarrhythmias often require locating in the heart the sites of origin ofthe arrhythmia or sites of abnormal conduction, and ablating these sitesthrough delivery of radiofrequency energy through an electrode locatedat or near the tip of a catheter. However, if the temperature of theelectrode and/or temperature of the immediately surrounding tissuebecome excessively high during such a procedure, the patient may sufferadverse consequences. In particular there is a risk of charring of thetissue in contact with the electrode, creating steam pops in the tissueand coagulating the surrounding blood. These undesired effects may leadto excess damage to the tissue compromising its physical integrity whichcould be catastrophic for the patient and/or increasing the risk of thepatient suffering a stroke as a result of coagulated blood or tissuefragments propagating through the blood stream to the patient's brain.It can be desirable to attempt to reduce the risk of such undesirableeffects by cooling the electrode and the tissue immediately surroundingthe electrode by delivering irrigation fluid through or around theelectrode. The irrigation fluid may exit through the electrode into theregion immediately surrounding the electrode. However, effectivelydelivering such irrigation to a remote tissue site within the human bodycan present challenges.

Accordingly, there remains a need for catheters having improvedirrigation and ablation abilities.

SUMMARY

Catheters having improved irrigation and ablation abilities are providedherein, as well as methods for treating tissue.

In one aspect, a catheter is provided that includes an elongate bodywith an electrode assembly on a distal end thereof. An actuator extendsthrough the elongate body and couples to the electrode assembly suchthat longitudinal movement of the actuator moves the electrode assemblybetween a collapsed configuration and an expanded configuration. Theelongate body has a fluid pathway extending therethrough for directingfluid to the electrode assembly. At least a portion of the fluid pathwayis coaxially disposed around at least a portion of the actuator and isfluidly sealed from the actuator.

There can be numerous variations of the catheter. For example, thecatheter can include a flexible seal disposed within the elongate bodyand around a portion of the actuator extending through the elongatebody. The flexible seal can define a fluid barrier between the actuatorand the fluid pathway in the housing. In another example, the flexibleseal can have a proximal end coupled to a proximal end of the elongatebody and a distal end coupled to the electrode assembly. In someembodiments, the elongate body can include first and second tubestherein, and the first and second tubes can be slidably coupled to oneanother and defining the fluid pathway. A flexible sleeve can also bedisposed around the first and second tubes such that a first end of thesleeve is sealed to the first tube and a second end of the sleeve issealed to the second tube, and the flexible sleeve can expand andcontract when the first and second tubes slide relative to one another.

In another example, the elongate body can include a tube that isconfigured to expand radially outward in a direction perpendicular to alongitudinal axis of the elongate body when the electrode assembly ismoved from the collapsed configuration to the expanded configuration. Instill another example, a proximal end of the tube can be attached to theelongate body and a distal end of the tube can be attached to theelectrode assembly, and the distal end of the tube can be fluidly sealedcircumferentially to the electrode assembly. In some examples, the tubecan be configured to bias the electrode assembly to the collapsedconfiguration. In another example, the tube comprises a metal braidcoated with a flexible sealing material.

In another aspect, a catheter is provided that includes an elongate bodyhaving a proximal end, a distal end, and a lumen extending between theproximal and distal ends. An end effector assembly is at least partiallydisposed within the distal end of the elongate body, and the endeffector assembly includes an expandable housing having a fluid sealedlumen therein. The housing has an inlet configured to allow fluid flowinto the fluid sealed lumen and has an electrode at a distal end thereofwith at least one fluid pathway extending therethrough that isconfigured to allow fluid flow out of the fluid sealed lumen. At leastone expandable member extends between the distal end of the elongatebody and the electrode, and the electrode is configured to distallyadvance and proximally retract relative to the elongate body to therebymove the housing between a collapsed configuration when the electrode isdistally advanced and an expanded configuration when the electrode isproximally retracted.

The catheter can have a number of variations. For example, the cathetercan include an actuator extending through the lumen in the elongate bodyand through the expandable housing of the end effector assembly. Theactuator can have a distal end coupled to the electrode, and theactuator can be configured to move proximally and distally relative tothe elongate body to distally advance and proximally retract theelectrode. In another example, the expandable housing can comprise firstand second tubes that are slidably coupled to one another and define thefluid sealed lumen.

In still another embodiment, the expandable housing can comprise a tubethat is configured to expand radially outward in a directionperpendicular to a longitudinal axis of the elongate body when thehousing is in the expanded configuration, and the tube can define thefluid sealed lumen. In one example, a proximal end of the tube can beattached to the distal end of the elongate body and a distal end of thetube can be attached to the electrode. In another example, the tube canbe configured to bias the expandable housing to the collapsedconfiguration. In still another example, the tube can be configured toblock energy passage across an outer surface thereof. In someembodiments, a volume inside the tube can change by about 25 percent orless when the housing moves between the collapsed and the expandedconfigurations.

In another aspect, a method for treating tissue is provided thatincludes advancing a catheter of an ablation device through a body lumento position a distal end of the catheter adjacent to tissue to betreated. The method also includes retracting an actuator extendingthrough the catheter to proximally retract an electrode coupled to adistal end of the actuator, and the proximal movement of the electrodecauses an expandable body to move from a collapsed configuration to anexpanded configured. The method also includes manipulating the catheterto position the electrode and the expandable body in contact with thetissue to be treated. The method includes actuating the ablation deviceto deliver energy to the electrode and to deliver fluid through at leastone fluid pathway extending through the electrode, and the fluid canflow through an expandable fluid channel at least partially defined bythe expandable body.

The method can have numerous variations. For example, retracting theactuator can cause first and second tubes of the expandable fluidchannel to slide relative to each other while maintaining the expandablefluid channel therethrough.

In another embodiment, the expandable body can includes a tube suchthat, when the expandable body moves from the collapsed configuration tothe expanded configured, the tube expands radially outward in adirection perpendicular to a longitudinal axis of the catheter. In oneexample, the expandable body can cover a part of the electrode not incontact with the tissue during delivery of energy to the electrode. Instill another example, the expandable body can block energy fromcrossing an outer surface of the expandable body during delivery ofenergy to the electrode. In one example, the method can includereleasing the actuator such that the expandable body reverts from theexpanded configuration to the collapsed configuration because theexpandable body is biased to the collapsed configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional, partially-perspective side view of oneembodiment of a distal end of a catheter with an end effector in adeployed, expanded, vector state;

FIG. 2 is a cross-sectional side view of the distal end of the catheterof FIG. 1 with the end effector in a collapsed, linear state;

FIG. 3 is a cross-sectional, partially-perspective side view of anotherembodiment of a distal end of a catheter with an end effector in adeployed, expanded state;

FIG. 4 is a cross-sectional, partially-perspective side view of anotherembodiment of a distal end of a catheter with an end effector in adeployed, expanded state;

FIG. 5 is a cross-sectional, partially-perspective side view of anotherembodiment of a distal end of a catheter with an end effector in adeployed, expanded state;

FIG. 6 is a cross-sectional, partially-perspective side view of anotherembodiment of a distal end of a catheter with an end effector in acollapsed, linear state; and

FIG. 7 is a cross-sectional side view of the distal end of the catheterof FIG. 6 with the end effector in a deployed, expanded state.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

Many ablation catheters have an expandable end effector that isconfigured to move from a collapsed, linear configuration duringdelivery to a deployed, expanded configuration once positioned adjacentto a tissue to be treated. In order to deploy the end effector, anactuator extends through the body of the catheter and it connected to aportion of the end effector such that advancement and/or retraction ofthe actuator moves the end effector between the collapsed and expandedconfigurations. During ablation, energy is delivered to the tissue toform a lesion. While energy alone can be effective at forming a lesion,there is a risk of overheating the electrode and burning and/or charringthe tissue. Accordingly, fluid can be delivered to the electrode to coolthe electrode during energy delivery, thereby reducing the risk ofcausing undesirable damage to the tissue. However, effectivelydelivering irrigation fluid to the electrode can be difficult when theelectrode used for delivery of the ablation energy or an electrodeassembly at the tip of the catheter is movable with respect to a shaftof the catheter. For example, a central ablation electrode in a catheterdisclosed in U.S. Pat. No. 8,882,761, filed Nov. 11, 2014 andincorporated herein in its entirety, is designed to be irrigated onlywhen the catheter is in a deployed configuration but not in a linearnon-deployed configuration or any time in between.

However, it can be desirable for the catheter to be able to be used forablation of cardiac tissue when it is in the linear configuration, inthe deployed configuration, or any configuration in between, and it canalso be desirable to be able to adequately irrigate the ablationelectrode(s) and immediately surrounding tissue in the linearnon-deployed configuration, in the deployed configuration, or anyconfiguration in between. This can be difficult to do so with manycatheters because an irrigation fluid compartment within the catheter isoften fixed with respect to a shaft of the catheter while the electrodeassembly is movable with respect to the catheter shaft. Thus a catheteris provided herein in which an irrigation fluid pathway in the catheteris coupled to an electrode assembly which moves with respect to a shaftof the catheter. Since ablation catheters are required to have extremelysmall diameters, fluid delivery through a catheter having an actuatorextending therethrough can be very challenging. More particularly,controlled and substantially constant flow of fluid to the electrode canbe challenging. Constant fluid flow is especially desirable for uniformcooling of electrodes and/or tissue and thereby uniform delivery of RFpower to the target site and creation of uniform lesions. Accordingly,various devices and methods are provided herein that allow fluid to becontinuously delivered to an expandable end effector assembly at asubstantially constant flow, while allowing an actuator to extendthrough the fluid pathway to couple to the end effector for deployingthe end effector. Such fluid channels can also be incorporated into socalled “basket” catheters, which involve a deployable basketincorporating a large number of electrodes to map electrically theentire inner surface of a cardiac chamber. It would be highly desirableto incorporate an ablation capability to such basket catheters, butagain the irrigation of the electrodes used for delivering the ablationenergy and the immediately surrounding tissue is difficult because ofthe need for coupling the irrigation fluid compartment in the catheterto the electrode assembly which moves with respect to the shaft of thecatheter. Thus expandable and contractible fluid channels, as discussedherein, can be incorporated to provide effective ablation and irrigationto basket catheters.

A person skilled in the art will appreciate that, while ablationcatheters are generally discussed herein, any catheter having anexpandable end effector can be used in combination with the variousfluid delivery techniques disclosed herein. In an exemplary embodiment,a catheter is provided with an elongate body that has a proximal end, adistal end, and a lumen extending therebetween. An end effector can beat least partially disposed within the distal end of the elongate body.The end effector can include an electrode at a distal end thereof withat least one fluid pathway extending therethrough. The end effector canalso include an expandable and contractible fluid channel or pathwaythat is configured to receive and direct fluid to the at least onepathway in the electrode. Various structures are provided herein fordefining the expandable and contractible fluid channel. The catheter canalso include at least one expandable member or wing extending betweenthe distal end of the elongate body and the electrode. In order toactuate the expandable member or wing, an actuator can extend throughthe elongate body and it can couple to the electrode. Longitudinalmovement of the actuator can distally advance and proximally retract theelectrode relative to the elongate body, which can cause the at leastone expandable member or wing to move between an initial collapsedconfiguration and a deployed expanded configuration. In order to allowcoupling between the actuator and the electrode, while still allow fluiddelivery to the electrode, the actuator can extend through the structuredefining the expandable and contractible fluid channel or pathway. Theactuator can, however, be fluidly sealed from the expandable andcontractible fluid channel or pathway to prevent fluid leakage. In use,movement of the actuator and electrode can cause expansion andcontraction of the fluid channel or pathway, which can remain sealed.Because the structure defining the expandable and contractible fluidchannel or pathway can expand and contract with movement of theelectrode, the fluid channel or pathway can be maintained and fluid canbe provided to the electrode at a substantially constant rate.

To achieve a substantially constant flow rate, it can be important tominimize or eliminate leaks. For example, couplings which leak mayresult in fluid moving out of a catheter compartment designed to containthe fluid into other elements of the catheter and/or into the tissue orblood surrounding the catheter. Fluid entering other elements of thecatheter can impair or block functioning of those elements. Also, it canbe helpful to closely control the amount of fluid delivered to cool oneor more ablation electrodes and the surrounding tissue to make a lesionsize predictable and the ablation procedure safe and effective. Thefluid flow can be controlled by controlling pressure of the fluidreservoir external to the body and/or monitoring a fluid flow rate outof that reservoir. Thus when a leak is present, a relationship betweenthe external pressure and externally measured fluid rate to the flowrate delivered to the desired locations to cool the electrode(s) andimmediately surrounding tissue can no longer be reliably determined. Forthese reasons any leak in the irrigation system is undesirable.

FIGS. 1 and 2 illustrate one embodiment of a distal end of a catheterwith an elongate body 100. The elongate body 100 can be flexible and canhave a proximal end, a distal end, and a lumen extending at leastpartially therethrough. An end effector 102 is disposed at leastpartially within the distal end of the elongate body 100. The endeffector 102 can include an expandable and contractible housing 200having a fluid inlet 302 at a proximal end and an electrode 400 at adistal end thereof and defining a fluid outlet in the form of at leastone pathway formed therethrough. A fluid delivery tube 300 can extendthrough the elongate body 100 for delivering fluid to the housing 200.The catheter can also include at least one expandable member or wing 600extending between the distal end of the elongate body 100 and theelectrode 400, and an actuator 700 coupled to the electrode foractuating the end effector 102. In this embodiment, proximal movement ofthe actuator 700 can cause the electrode 400 to retract proximally,thereby causing the expandable member or wing(s) 600 to expand, as shownin FIG. 1, and distal movement of the actuator can cause distaladvancement of the electrode body 100, which can cause the expandablemember or wing(s) 600 to collapse or compress into a linearconfiguration, as shown in FIG. 2. For example, the catheter with theelongate body 100 can be maneuvered to a surgical site in the collapsed,linear configuration, as shown in FIG. 2. When at a treatment site, thecatheter can either treat tissue in the linear configuration or it canbe deployed into the expanded configuration, as shown in FIG. 1.

The end effector can have a variety of configurations, but as indicatedabove the end effector is preferably configured to allow advancement andretraction of the electrode using the actuator, while also allowingfluid to be delivered to the electrode. In the illustrated embodiment,the expandable and contractible housing 200 forms a proximal portion ofthe end effector with the electrode positioned at the distal endthereof. The expandable and contractible housing 200 can have a varietyof configurations, but in an exemplary embodiment it is at leastpartially disposed in the elongate body 100 and at least a portion of itcan be configured to move relative to and extend from the distal end ofthe elongate body 100. The housing 200 can be positioned co-axially withthe elongate body 100 such that a longitudinal axis of the housing 200corresponds to a longitudinal axis A1 of the elongate body 100. In orderto define a fluid sealed lumen 206 extending therethrough, a distal end204 of the housing 200 can be fixed to the electrode 400, and a proximalend 202 of the housing 200 can be sealed by and fixed within theelongate body 100. For example, a heat treatment can be applied to theelongate body to form a substantial end cap 800 on the housing 200, aswill be discussed in more detail below. As indicated above, the housing200 can be configured to expand and contract as the electrode 400 ispulled proximally and pushed distally during use. As illustrated in FIG.1, the housing 200 can include an upper shaft or tube 210, a lower shaftor tube 212, and an expansion member 214. A proximal end of theexpansion member 214 can be attached to the upper shaft 210, and adistal end of the expansion member 214 can be attached to the lowershaft 212. The upper shaft 210 can be fixed at its proximal end to theelongate body 100 and the lower shaft 212 can be fixed to the electrode400, and one of the upper and lower shafts 210, 212 can be slidablydisposed within the other one of the upper and lower shafts 210, 212. Asa result, the lower shaft 212 can be configured to slidably move towardsand away from the upper shaft 210 in coordination with to movement ofthe electrode 400. Such a configuration allows the housing 200 to expandand contract. As shown in FIG. 1, a distal end of the upper shaft 210and a proximal end of the lower shaft 212 overlap one another when thehousing 200 is in a deployed state. As shown in FIG. 2, the upper shaft210 and the lower shaft 212 are moved away from each other in a linearstate.

While the upper and lower shafts 210, 212 can be configured to sealingengage one another to prevent fluid leakage from the housing 200, in anexemplary embodiment the expansion member 214 forms a seal around theengagement portion between the two shafts 210, 212. The expansion member214 can be configured to expand between the two shafts 210, 212 as theshafts 210, 212 slidably move away from each other, and to compress asthe shafts 210, 212 move toward one another. The expansion member 214will thus allow movement of the shafts 210, 212 while maintaining a sealin the fluid sealed lumen 206 within the housing 200 when the housing isin the expanded state or the contracted state. In certain aspects, alength of each of the shafts 210, 212 can be minimized because theexpansion member 214 can prevent disengagement between the shafts 210,212 in the expanded state while still providing a fluid sealed lumen 206in the housing 200. Because lengths of the shafts 210, 212 can beminimized, an overall length of the housing 200 can be minimized, whichallows for a smaller overall end effector length and thus moreflexibility of the catheter.

The shafts 210, 212 can be made of stiffer materials relative to theexpansion member 214, such as plastics, elastomers, metals, etc., andthe expansion member 214 can be made of stretchable and compressiblematerial, such as balloon-like materials, elastomers, plastics, etc. Theexpansion member 214 can have a variety of forms. For example, theexpansion member 214 can be a stretchable, elastic tube. In somesituations, a volume of an elastic tube can change when it is stretched,which can result in blood being sucked into the catheter when thecatheter configuration is moved between a deployed state and a linearstate. This can result in the formation of clots in the fluidcompartment. Such clots might subsequently be expelled into the bloodstream. Thus it can be helpful to provide support to the elastic tube byproviding a support structure, using a more rigid material, etc. Theexpansion member 214 can be made of a more rigid material that can befolded accordion style. The internal volume of such a tube canexperience less change when its length is altered compared to an elastictube. However, when its length is shortened, the expansion member 214can potentially fold over on itself, thus impeding fluid flow throughthe catheter. The expansion member 214 can thus have a centrallongitudinal support element therein to provide support and preventincorrect folding and/or collapse. For example, one or both of theshafts 210, 212 can also serve as supports to the expansion member 214when the housing 200 moves to the contracted state, allowing theexpansion member 214 to fold in an orderly controlled manner, similar toan accordion, rather than collapsing in on itself and potentiallyblocking the fluid sealed lumen 206 of the housing 200. However, thecentral longitudinal support element is not limited to one or both ofthe shafts 210, 212. For example, the central longitudinal supportelement can include one or more other catheter elements, such as theactuator 700, a wire connected to a temperature sensor (such as athermocouple) located in a tip of the catheter, a tube containing theactuator and/or thermocouple wire, etc. Because the stretchable tube isprevented from folding over on itself, fluid flow through the catheterin general and the expansion member 214 in particular is not impeded bysuch folding. In addition, in embodiments where the central longitudinalsupport element is a tube containing other catheter elements, such asthe actuator wire or the wire connected to a thermocouple, these otherelements can be isolated from the irrigation fluid and thus any adverseeffects on the function of these elements that would result from contactwith the irrigation fluid can be minimized. In some embodiments, aportion of the central longitudinal support element itself can include astretchable element that can serve to reduce or prevent leaks around theactuator wire and/or thermocouple wire. A variety of other supports canbe used with the expansion member 214, such as tubes, braces, stiffermaterials, pre-formed or folded material that will maintain a more rigidaccordion fold when contracted, etc. The fluid sealed lumen 206 can beconfigured to allow delivery of fluid to the electrode 400 with moreconsistent flow rates and more ideal fluid pressures, thus helping toprovide a smoother function of the device and better irrigation andablation of tissue.

As indicated above, the proximal end 202 of the housing 200 can becoupled to the elongate body 100, and can be fluidly sealed to preventany fluid from moving proximally from the fluid sealed lumen 206 of thehousing into other proximal parts of the catheter. The proximal end 202of the housing 200 can be coupled to the elongate body 100 through avariety of means. For example, the elongate body 100 can be heattreated, causing the elongate body 100 to melt around and across an openproximal end of the housing 200, as well as around other componentsextending therethrough, such as the fluid delivery tube 300 and asealing shaft 500 that receives the actuator. The process of heating canseal the proximal end 202 of the housing 200, as shown in FIG. 1,forming a cap 800 of melted material and achieving fixation and a fluidseal through one process. A variety of other means for both fixation andsealing can be used, however. For example, the proximal end 202 of thehousing 200 can be sealed using a cover, a separate and distinct cap,seal, etc., placed across the opening of the proximal end 202 of thehousing 200. An end cap or cover can also be formed as part of the uppertube.

As indicated above, the housing 200 is configured to receive fluidtherein and to direct fluid to the electrode. Fluid can be introduced tothe housing 200 through a variety of means, such as via a fluid deliverytube 300 extending through an inlet formed in the sealed proximal end ofthe housing 200. The fluid delivery tube 300 can be configured todeliver fluid through the catheter and into the fluid sealed lumen 206of the housing 200. The fluid delivery tube 300 can at least partiallyextend through the catheter and the elongate body 100, for exampleextending from a proximal end of the catheter and terminating in thefluid sealed lumen 206 of the housing 200. The cap 800 can be formedafter the fluid delivery tube 300 is in place, thus sealing the proximalend 202 of the housing 200 and securing the fluid delivery tube 300 inplace. However, the fluid delivery tube 300 can be configured to passthrough a variety of covers over the proximal end 202 of the housing 200and can be secured in place through a variety of means, such as by useof adhesive or pins. The fluid delivery tube 300 can be configured todeliver a consistent flow of fluid into the fluid sealed lumen 206.

The electrode 400 can be positioned at a distal end of the elongate body100, and it can be configured to move between a proximally deployed orvector position, as illustrated in FIG. 1, to an advanced or linearposition, as illustrated in FIG. 2. In the retracted position, theelectrode 400 can be at least partially retracted into the elongate body100, and in the expanded position, the electrode 400 can extend distallyaway from the distal-most end of the elongate body 100. A proximal endof the electrode 400 can be at least partially disposed in the distalend 204 of the expandable and contractible housing 200, expandable alongits longitudinal dimension such that it is stretchable. For example, thelower shaft 212 of the housing 200 can attach to the electrode 400 suchthat a fluid seal can be formed along the engagement of the electrode400 and the lower shaft 212. This engagement can seal the distal end ofthe fluid sealed lumen 206 of the housing 200. The electrode 400 can beconfigured to be moved distally and proximally, which can cause thehousing 200 to expand and contract as the lower shaft 212 moves distallyand proximally with the electrode 400. The electrode 400 can have one ormore fluid paths therethrough configured to allow fluid flow from thefluid sealing lumen 206 to a position distally external from the entirecatheter to reach tissue to be irrigated and/or ablated. For example,the electrode 400 can have one or more inlet ports 402 on a proximalhalf thereof that open inside of the fluid sealed lumen 206 of thehousing 200 and connect via one or more fluid channels within theelectrode 400 to outlet ports 404 on a distal half thereof that openoutside of the catheter entirely. The electrode 400 can thus beconfigured to receive fluid through the inlet ports 402 from the fluidsealed lumen 206 of the housing 200 and can be configured to expel thefluid from the outlet ports 404 to tissue that is distally positioned infront of the electrode 400. Because the electrode 400 can be sealed tothe housing 200 at the distal end of the fluid sealed lumen 206 andbecause the housing 200 can expand and contract with the electrode 400,irrigation can be performed when the electrode 400 is retracted oradvanced (e.g. in either of the deployed or linear states shown in FIGS.1 and 2).

In order to move the electrode, the end effector 102 can be actuatedthrough a variety of means, such as by use of the actuator 700illustrated in FIG. 1. The actuator 700 can have a variety of forms,such as one or more wires and/or cables. The actuator 700 can extendthrough the elongate body 100 between a proximal end of the catheter andthe end effector 102. As illustrated in FIG. 1, the actuator 700 canextend through the lumen 206 of the housing 200 and can be fixed to aproximal end of the electrode 400. The actuator 700 can be slidablerelative to the elongate body 100 such that the actuator 700 can slidedistally and proximally while the elongate body 200 remains unmovedrelative to the actuator 700. The actuator 700 can be in the form of awire that is rigid enough to push the electrode 400 distally into theextended state illustrated in FIG. 2, and strong enough to pull theelectrode 400 proximally into the retracted state illustrated in FIG. 1,while still being flexible enough to extend through bending and angledsections of the catheter. The actuator 700 can include anelectrically-conductive wire that can deliver energy to the electrode400 during tissue ablation. The actuator 700 can also have one or morecoatings thereon to protect surrounding components from the electricalenergy deliverable through the actuator 700 and to protect the actuator700 from its surrounding environments.

In order to allow the actuator to couple to the electrode, the actuator700 can be co-axial with the housing 200. The actuator 700 can beconfigured to extend through the proximal end 202 of the housing 200 andthrough the fluid sealed lumen 206 to engage with the proximal end ofthe electrode 400 such that the actuator 700 is slidable relative to theproximal end 202 of the housing 200 while the fluid seal of the fluidsealed lumen 206 is maintained. The fluid seal of the fluid sealed lumen206 can be maintained even with the slidable actuator 700 disposedtherein through a variety of means. For example, a sealing shaft 500 canextend around at least a portion of the actuator 700 and can beconfigured to create a fluid barrier between the actuator 700 and fluidin the end effector 102, such as the fluid sealed lumen 206. The sealingshaft 500 can extend at least partially through the end effector 102,for example extending from the electrode 400, through the fluid sealedlumen 206 of the housing 200, to the proximal end 202 of the housing200, and optionally into the proximal part of the catheter. The actuator700 can extend through a lumen within the sealing shaft 500, and thesealing shaft 500 can thus prevent the fluid in the fluid sealed lumen206 of the housing 200 from contacting the actuator 700. For example, adistal end of the sealing shaft 700 can be sealably fixed to theproximal end of the electrode 400, and a proximal end of the sealingshaft 500 can extend into and optionally through the proximal end 202 ofthe housing. The sealing shaft 500 can be fixed in place relative to theproximal end 202 of the housing 200. For example, when the cap 800 isformed, the sealing shaft 500 can be positioned before formation andfixed in place relative to the proximal end 202 of the housing duringcap formation. However, the sealing shaft 500 can also be fixed in placethrough a variety of other means, such as adhesives, pins, engagementwith other seals, caps, or covers added to the proximal end 202 of thehousing 200, etc.

The sealing shaft 500 can be configured to expand and contract with thehousing 200 as the electrode 400 is moved distally and proximally.Because the sealing shaft 500 is able to expand and contract withmovement of the electrode 400, the sealing shaft 500 can be configuredto provide a sealed passage for the actuator 700 through the fluidsealed lumen 206 of the housing 200, which can protect the actuator 700and can allow the lumen 206 in the housing 200 to remain fluid sealedeven as the actuator 700 is moved back and forth through the proximalend 202 of the housing 200. Without the sealing shaft 500, pressure fromthe fluid flowing into the housing 200 could cause fluid to flow throughthe opening in the proximal end 202 of the housing 200 around theactuator 700, and into the rest of the catheter. The required movementof the actuator 700 through the proximal end 202 of the housing 200makes fluidly sealing the proximal end 202 through other means, such asby use of O-rings, difficult to achieve and consistently maintain. Inparticular, O-rings or other seals will create friction, therebypreventing movement of the actuator. Accordingly, the sealing shaft 500allows for free movement of the actuator 700, while fluidly separatingthe actuator 700 from the fluid sealed lumen 206 of the housing 200,thus allowing fluid to be delivered directly to the electrode.

The sealing shaft 500 can include a flexible sealing portion that isconfigured to expand and contract with movement of the actuator 700 andthe electrode 400. In the illustrated embodiment, a sealing member 502forms a distal portion of the sealing shaft 500 and is sealed on itsdistal end to the proximal end of the electrode 400. The proximal end ofthe sealing member 502 can be sealed to a rigid portion 504 of thesealing shaft 500 that can extend through the proximal end 202 of thehousing 200. However, the sealing member 502 can also be sealed directlyto the proximal end 202 of the housing 200 and/or a cap, cover, seal,etc. that is used to close the proximal end 202. Alternatively, thesealing member 502 can be integral and unitary with the sealing shaft500.

When the actuator 700 is moved proximally and distally to move theelectrode 400 between the contracted and the expanded states, thesealing member 502 is configured to stretch and contract with movementof the actuator 700 so that the electrode 400 can be moved withoutbreaking the fluid barrier between the fluid sealed lumen 206 of thehousing 200, the proximal end 202 of the housing 200, and the actuator700. The sealing member 502 can be made from any material that canexpand and contract, such as various elastomers, plastics, elastics,balloon-like materials, etc. The sealing shaft 500 can also have a rigidportion 504 that extends through the proximal end 202 of the housing 200and that is configured to be secured in place by the cap 800. The rigidportion 504 can be made of a variety of materials that are configured towithstand the heat treatment applied to the elongate body, such asvarious plastics or metals.

As indicated above, the catheter also includes at least one expandablemember extending between the electrode and the distal end of theelongate body. In an exemplary embodiment, the catheter can include fourexpandable members positioned equidistant there around. As the electrode400 advances and retracts, the expandable members 600 that extendsbetween the distal end of the elongate body 100 and the electrode 400moves between an initial linear configuration for advancement through abody lumen, to flared or expanded configuration. In the deployedconfiguration, the expandable members can bend around a midpoint therealong to extend substantially perpendicular relative to the elongatebody 100, as illustrated in FIG. 1, forming a flower pedal shape orpropeller blade shape around the electrode 400. The one or moreexpandable members 600 can be configured to extend longitudinallyrelative to the elongate body 100 when the electrode 400 is extendeddistally away from the elongate body 100, as illustrated in FIG. 2. Asthe electrode 400 and the distal end 204 of the housing 200 extenddistally, the expandable members 600 can be configured to flattenagainst an exterior surface of the housing 200 as the distal end of thecatheter takes on a linear shape, as illustrated in FIG. 2. The distalends of the one or more expandable members 600 can couple to theelectrode 400 at a point between the proximal and distal end of theelectrode 400, such as at a point corresponding to the engagementbetween the distal end 204 of the housing 200 and the electrode 400.

The expandable members 600 can each have one or more electrodes disposedthereon and positioned on a distal portion of the expandable member 600such that each electrode is configured to be approximately perpendicularto the elongate body 100 when the electrode 400 is retracted in thecontracted state illustrated in FIG. 1 and each expandable member 600 isin a flared or winged state. The one or more electrodes on theexpandable members 600 can be configured to operate in coordination withelectrode 400 to provide ablation to a larger surface area of tissuethan just the electrode 400 alone. Additional details concerning thecatheter generally and the interaction between the expandable member(s)and a central electrode are discussed in detail in U.S. Pat. No.8,882,761, filed Jul. 15, 2008, U.S. Pat. No. 9,717,558, filed Nov. 7,2014, and patent application Ser. No. 15/661,606, filed Jul. 27, 2017,all of which are hereby incorporated by reference herein in theirentireties. The electrode(s) on the one or more expandable members 600can be coupled to and receive energy from the actuator 700.

In use, the end effector 102 can be arranged in the linear state asshown in FIG. 2 and the catheter can be advanced through a body lumen ofa patient to position the end effector 102 at a surgical site withtissue to be treated, such as tissue requiring ablation and/orirrigation. The actuator 700 can be proximally retracted to proximallyretract the electrode 400, causing the end effector 102 to move to thedeployed state, as illustrated in FIG. 1, with the expandable members inthe expanded configuration. As the electrode 400 is retracted, thehousing 200 compresses and reduces in length as the shafts 210, 212 movetowards each other and overlap with one another and the expansion member214 contracts before folding over one or both of the shafts 210, 212 asit compresses entirely. The sealing member 502 of the sealing shaft 500can also begin compressing and folding together as the actuator 700retracts the electrode. The catheter can be manipulated to position theelectrode 400 and one or more of the expandable members 600 in contactwith tissue to be treated. The catheter can be actuated to deliverenergy to the electrode 400 and any electrodes arranged on theexpandable members 600 and/or to deliver fluid through at least onefluid pathway in the electrode 400. The fluid can flow through the fluidsealed lumen 206 and through the ports 402, 404 in the electrode. Whenablation and/or irrigation is finished, the actuator 700 can be pusheddistally to cause the end effector 102 to return to the linear state.The housing 200 can expand in length as the shafts 210, 212 move awayfrom each other and the expansion member 214 expands to keep the shafts210, 212 engaged with each other while allowing the shafts 210, 212 tomove away. The sealing member 502 of the sealing shaft 500 also canunfold and expand as the electrode 400 moves distally. The catheter canbe maneuvered to another site or removed from the patient. Because ofthe expandable and contractible fluid channel in the end effector 102,fluid can be successfully delivered to tissue with the end effector 102in the expanded state, allowing ablation with fluid and/or irrigation tobe performed successfully in the expanded state. The catheter(s)disclosed herein can be steered through a variety of means, which arewell-known in the art.

Catheters with expandable and contractible fluid pathways extendingtherethrough can have a variety of other configurations. For example,FIG. 3 illustrates a catheter with an expandable and contractible fluidpathway similar to the catheter of FIGS. 1 and 2. FIG. 3 illustrates adistal end of a catheter with an elongate body 1000. The elongate body1000 can have a proximal end, a distal end, and a lumen extending atleast partially therethrough. An end effector 1102 is disposed at leastpartially within the distal end of the elongate body 1100, similar tothe end effector 102 of FIGS. 1 and 2. The end effector 1102 can includean expandable and contractible housing 1200 having a fluid delivery tube1300 and an electrode 1400 at a distal end thereof and defining a fluidoutlet. An expandable and contractible sealing shaft 1500 can extendwithin the housing 1200 from a proximal end to the distal end. Thedevice can also include at least one expandable member or wing 1600extending between the distal end of the elongate body 1100 and theelectrode 1400. An actuator 1700 can also extend through the device andit can be configured to actuate the end effector 1102. Upon actuation ofthe actuator 1700, the electrode 1400 can be configured to distallyadvance and proximally retract relative to the elongate body 1100, whichcan cause the expansion and the contraction of various components withinthe elongate body.

The expandable and contractible housing 1200 can be similar to thehousing 200, having a fluid sealed lumen 1206 therethrough. The housing1200 can include an upper shaft 1210, a lower shaft 1212, and anexpansion member 1214. A proximal end of the expansion member 1214 canbe attached to a distal end of the upper shaft 1210, and a distal end ofthe expansion member 1214 can be attached to a proximal end of the lowershaft 1212. The upper shaft 1210 can be sealably fixed at a proximal endto the elongate body 1100, such as at a melted cap 1800, and the lowershaft 1212 can be sealably fixed to the electrode 1400. The upper andlower shafts 1210, 1212 can be configured to move towards and away fromeach other upon movement of the electrode 1400. However, the shafts1210, 1212 can be configured not to overlap each other. Instead, theexpansion member 1214 can extend therebetween, and a support shaft 1216can have a proximal end fixed to a proximal point in the elongate body1100, similar to the upper shaft 1210, and the support shaft 1216 canextend distally within the housing 1200 to provide support to theexpansion member 1214 (instead of support being provided by the upperand/or lower shafts 210, 212 as provided in FIGS. 1 and 2). The supportshaft 1216 can terminate at a point distal of the expansion member 1214when the expansion member 1214 is in its contracted state so that theexpansion member 1214 can fold in an orderly, controlled way, like anaccordion, as it contracts rather than collapsing in on itself andpotentially blocking the fluid sealed lumen 1206 of the housing 1200.

While the support shaft 1216 is fixed in a proximal position in FIG. 3,the support shaft can be attached at various positions. For example,FIG. 4 illustrates a catheter with an elongate body 2100 and anexpandable and contractible fluid pathway similar to the catheters ofFIGS. 1 and 3. In this embodiment, the support shaft 2216 can have adistal end fixed to a proximal portion of the electrode 2400, similar tothe lower shaft 2212, and the support shaft 2216 can extend proximallywithin the housing 2200 to provide support to the expansion member 2214.The support shaft 2216 can terminate at a point proximal of theexpansion member 2214 when the expansion member 2214 is in itscontracted state so that the expansion member 2214 can fold in anorderly, controlled way, like an accordion, as it contracts rather thancollapsing in on itself and potentially blocking the fluid sealed lumen2206 of the housing 2200.

The expansion member can also be configured such that no supportstructure is required. For example, FIG. 5 illustrates a catheter withan expandable and contractible fluid pathway similar to the catheters ofFIGS. 1-4. FIG. 5 illustrates a distal end of a catheter with anelongate body 3100. The elongate body 3100 can have a proximal end, adistal end, and a lumen extending at least partially therethrough. Anend effector 3102 is disposed at least partially within the distal endof the elongate body 3100, similar to the end effector 102 of FIGS. 1and 2. The end effector 3102 can include an expandable and contractiblehousing 3200, a fluid delivery tube 3300, and an electrode 3400 at adistal end thereof. An expandable and contractible sealing shaft 3500can extend within the housing 3200 from a proximal end to the distalend. The catheter can also include at least one expandable member orwing 3600 extending between the distal end of the elongate body 3100 andthe electrode 3400, and an actuator 3700 extending through the elongatebody and configured to actuate the end effector 3102. Upon actuation ofthe actuator 3700, the electrode 3400 can be configured to distallyadvance and proximally retract relative to the elongate body 3100, whichcan cause the expansion and the contraction of various components withinthe elongate body.

The expandable and contractible housing 3200 can be similar to thehousing 200, having a fluid sealed lumen 3206 therethrough. The housing3200 can include an upper shaft 3210, a lower shaft 3212, and anexpansion member 3214. However, the expansion member 3214 can beconfigured to be rigid enough not to collapse in on itself while stillbeing able to contract and expand. For example, the expansion member3214 can be formed of semi-rigid panels that are configured to fold inan accordion style as they contract and extend linearly as they expand.

The expandable and contractible housing can also be configured in theform of a flexible tube. For example, FIGS. 6 and 7 illustrate acatheter with an expandable and contractible fluid pathway similar tothe catheters of FIGS. 1-4. FIGS. 6 and 7 illustrate a distal end of acatheter with an elongate body 4100. The elongate body 4100 can have aproximal end, a distal end, and a lumen extending at least partiallytherethrough. An end effector 4102 is disposed at least partially withinthe distal end of the elongate body 4100, similar to the end effector102 of FIGS. 1 and 2. The end effector 4102 can include an expandableand contractible housing 4200, a fluid delivery tube 4300, and anelectrode 4400 at a distal end thereof. An expandable and contractiblesealing shaft 4500 can extend within the housing 4200 from a proximalend to the distal end. The catheter can also include at least oneexpandable member or wing 4600 extending between the distal end of theelongate body 4100 and the electrode 4400, which in various embodimentscan have one or more peripheral electrodes thereon. An actuator 4700 canextend through the elongate body and it can be configured to actuate theend effector 4102. Upon actuation of the actuator 4700, the electrode4400 can be configured to distally advance and proximally retractrelative to the elongate body 4100, which can cause the expansion andthe contraction of various components within the elongate body. Forexample, distal movement of the actuator 4700 can cause distaladvancement of the electrode 4400, which can cause the expandable memberor wing(s) 4600 to collapse or compress into a linear configuration, asshown in FIG. 6, and proximal movement of the actuator 4700 can causethe electrode 4400 to retract proximally, thereby causing the expandablemember or wing(s) 4600 to expand, as shown in FIG. 7.

The expandable and contractible housing 4200 can be similar to housing200, creating a fluid sealed lumen 4206 therethrough. However, theexpandable and contractible housing 4200 in this embodiment is in theform of a flexible tube that expands radially outward in a directionperpendicular to a longitudinal axis A2 of the housing 4200 as thehousing 4200 is compressed in a direction parallel to the axis A2. Insome embodiments, when the actuator 4700 is actuated to pull theelectrode 4400 proximally and to move the at least one wing 4600 to anexpanded configuration (such as illustrated in FIG. 7), the housing 4200can be configured such that it remains within a space within the atleast one expanded wing 4600. A proximal end of the housing 4200 can besealably fixed to a proximal end of the elongate body 4100, such as at amelted cap 4800, and a distal end of the housing 4200 can be sealablyfixed to the electrode 4400 at a location distal to fluid inlet ports4402 and proximal to fluid outlet ports 4404 in the electrode 4400. Thehousing 4200 can be sealably fixed circumferentially around theelectrode 4400 so that fluid cannot leak from the lumen 4206 inside thehousing 4200 to any space outside the housing 4200.

In various embodiments, the expandable and contractible housing 4200 canbe in the form of a flexible tube with a smooth surface both in acollapsed, linear configuration, as shown in FIG. 6, and in an expanded,deployed configuration, as shown in FIG. 7. The smooth surface of theflexible tube can have a low likelihood of trapping any material, suchas blood or tissue, as trapped blood or tissue material can potentiallyclot and form small emboli that would pose a risk to the patient. Thehousing 4200 can be made of a variety of materials. For example, thehousing can be formed from a flexible braid, such as flexible metalbraids, and in some embodiments, the metal braid can be coated with aflexible sealing material so that fluid does not pass through a wall ofthe housing. The flexible braids can be made of a variety of materials.For example, the metal braid can be constructed from steel strandsand/or nitinol strands. In some embodiments, nitinol strands can be usedto allow the housing to revert to a pre-determined shape when externalforces are not acting upon it. For example, the housing can be biased tothe collapsed, linear configuration. The flexible sealing material caninclude a variety of materials, such as a plastic and/or rubber material(like silicone) that is deposited on the metal braid. The combination ofmetal braids and flexible sealing materials can allow the housing towithstand a pressure of fluid contained within the lumen 4206 of thehousing 4200 while the housing 4200 remains flexible, allowing thehousing 4200 to be rigid enough not to collapse in on itself while stillbeing able to contract and expand. Thus, in some embodiments, thehousing 4200 can define the lumen 4206. In some embodiments, theproximal portion of the housing 4200 is covered by a rigid plasticsleeve in order to constrain the proximal portion of the housing tomaintain a cylindrical shape as shown in FIG. 7. Furthermore, the coatedmetal braid can cover a portion of the electrode 4400 not in directcontact with tissue, for example covering at least some or all of theelectrode 4400 not in direct contact with tissue, and thereby can serveas a Faraday cage, blocking energy from spreading to blood and tissuenot in direct contact with the electrode 4400. Such a spread of energyto non-targeted regions can potentially be undesirable from efficacy,efficiency, and patient safety perspectives. Thus, the majority or allof the energy can be directed instead through the electrode 4400 andinto tissue.

In some embodiments, the housing 4200 can be configured so that a volumeof fluid inside the lumen 4206 experiences little to no change when thehousing 4200 moves between its collapsed and expanded configurations.For example, the volume of the lumen 4206 can change less than about 50percent, and more preferably less than about 25 percent, and even morepreferably less than about 10 percent. The volume remainingsubstantially unchanged can be caused by, for example, the braided andcoated construction of the housing 4200, which permits the housing 4200to change drastically in shape (such as moving from the collapsedconfiguration to the expanded configuration) while minimizing loss ininternal volume. Allowing minimal change to the volume of the lumen 4206can help to minimize an amount of fluid entering and/or being expelledfrom the lumen 4206 when the housing 4200 is moved between the collapsedand expanded configurations. Minimizing the amount of fluid enteringand/or being expelled from the lumen 4206 when the housing 4200 movesbetween its collapsed and expanded configurations can be helpful becausesuch changes in volume might involve blood entering and being expelledfrom the housing 4200, and such blood might potentially clot and formemboli that can pose a risk to a patient.

In various embodiments, the expandable and contractible housing can beconfigured and constructed of material that will spontaneously revert toa pre-specified form when external forces are not acting upon it, suchas nitinol as mentioned above. For example, the housing 4200 can beconstructed to revert to an elongated cylindrical form when an externalforce is not compressing it along the direction parallel to the axis A2of the housing 4200. In such an embodiment, when the actuator 4700 isreleased from retracting the electrode 4400 proximally, the housing 4200will elongate and consequently the elongate body 4100 will revert to thecollapsed, linear configuration, shown in FIG. 6. By causing the housing4200 to revert to an elongated cylindrical form, any wire used for theactuator 4700 does not need to be as stiff because a user, after usingthe electrode 4400 in the expanded configuration, would not need to beable to push the electrode 4400 distally into the collapsedconfiguration. If the user were required to push the actuator 4700distally to cause the electrode 4400 to move distally, the wire wouldneed to be made from a thick, relatively stiff material. A thicker wirecan take up more space inside the catheter, which in turn may require acatheter having a larger diameter. This is undesirable as such acatheter can potentially be more difficult to maneuver through narrowblood vessels, and a larger catheter could potentially create a largeropening if the catheter were intentionally pushed through normallyclosed biological structure, such as the foramen ovale. Additionally, astiffer wire can potentially make the entire catheter stiffer and lessflexible, which may make it more difficult to maneuver the catheterinside a body of a patient. In various embodiments, the housing can bethe flexible tube itself, and in other embodiments, the housing cansurround the flexible tube such that the flexible tube as describedabove is within the housing.

A person skilled in the art will appreciate that, while not shown, anyhandle assembly known in the art can be used in combination with thecatheter assemblies disclosed herein. The handle assembly can includeany number of features, such as steering mechanisms for steering thecatheter, actuation knobs, levers, buttons or the like for controllingthe actuator, and for controlling fluid and energy delivery.

In the present disclosure, like-numbered components of the embodimentsgenerally have similar features, and thus within a particular embodimenteach feature of each like-numbered component is not necessarily fullyelaborated upon. Sizes and shapes of the devices described herein, andthe components thereof, can depend at least on the anatomy of thesubject in which the devices will be used, the size and shape ofcomponents (e.g., spinal rods) with which the devices will be used, andthe methods and procedures in which the devices will be used. Thefigures provided herein are not necessarily to scale. Although thedevices and methods disclosed herein are generally directed to surgicaltechniques, they can also be used in applications outside of thesurgical field. Although the invention has been described by referenceto specific embodiments, it should be understood that numerous changesmay be made within the spirit and scope of the inventive conceptsdescribed. Accordingly, it is intended that the invention not be limitedto the described embodiments, but that it have the full scope defined bythe language of the following claims.

What is claimed is:
 1. A catheter, comprising: an elongate body having an electrode assembly on a distal end thereof, an actuator extending through the elongate body and coupled to the electrode assembly such that longitudinal movement of the actuator moves the electrode assembly between a collapsed configuration and an expanded configuration, the elongate body having a fluid pathway extending therethrough for directing fluid to the electrode assembly, at least a portion of the fluid pathway being coaxially disposed around at least a portion of the actuator and being fluidly sealed from the actuator.
 2. The catheter of claim 1, further comprising a flexible seal disposed within the elongate body and around a portion of the actuator extending through the elongate body, the flexible seal defining a fluid barrier between the actuator and the fluid pathway in the housing.
 3. The catheter of claim 2, wherein the flexible seal has a proximal end coupled to a proximal end of the elongate body and a distal end coupled to the electrode assembly.
 4. The catheter of claim 1, wherein the elongate body includes first and second tubes therein, the first and second tubes being slidably coupled to one another and defining the fluid pathway, and wherein a flexible sleeve is disposed around the first and second tubes such that a first end of the sleeve is sealed to the first tube and a second end of the sleeve is sealed to the second tube, and the flexible sleeve expands and contracts when the first and second tubes slide relative to one another.
 5. The catheter of claim 1, wherein the elongate body includes a tube that is configured to expand radially outward in a direction perpendicular to a longitudinal axis of the elongate body when the electrode assembly is moved from the collapsed configuration to the expanded configuration.
 6. The catheter of claim 5, wherein a proximal end of the tube is attached to the elongate body and a distal end of the tube is attached to the electrode assembly, and the distal end of the tube is fluidly sealed circumferentially to the electrode assembly.
 7. The catheter of claim 5, wherein the tube is configured to bias the electrode assembly to the collapsed configuration.
 8. The catheter of claim 5, wherein the tube comprises a metal braid coated with a flexible sealing material.
 9. A catheter, comprising: an elongate body having a proximal end, a distal end, and a lumen extending between the proximal and distal ends; an end effector assembly at least partially disposed within the distal end of the elongate body, the end effector assembly including an expandable housing having a fluid sealed lumen therein, the housing having an inlet configured to allow fluid flow into the fluid sealed lumen and having an electrode at a distal end thereof with at least one fluid pathway extending therethrough and configured to allow fluid flow out of the fluid sealed lumen; and at least one expandable member extending between the distal end of the elongate body and the electrode; wherein the electrode is configured to distally advance and proximally retract relative to the elongate body to thereby move the housing between a collapsed configuration when the electrode is distally advanced and an expanded configuration when the electrode is proximally retracted.
 10. The catheter of claim 9, further comprising an actuator extending through the lumen in the elongate body and through the expandable housing of the end effector assembly, the actuator having a distal end coupled to the electrode, the actuator being configured to move proximally and distally relative to the elongate body to distally advance and proximally retract the electrode.
 11. The catheter of claim 9, wherein the expandable housing comprises first and second tubes slidably coupled to one another and defining the fluid sealed lumen.
 12. The catheter of claim 9, wherein the expandable housing comprises a tube that is configured to expand radially outward in a direction perpendicular to a longitudinal axis of the elongate body when the housing is in the expanded configuration, the tube defining the fluid sealed lumen.
 13. The catheter of claim 12, wherein a proximal end of the tube is attached to the distal end of the elongate body and a distal end of the tube is attached to the electrode.
 14. The catheter of claim 12, wherein the tube is configured to bias the expandable housing to the collapsed configuration.
 15. The catheter of claim 12, wherein the tube is configured to block energy passage across an outer surface thereof.
 16. The catheter of claim 12, wherein a volume inside the tube changes by about 25 percent or less when the housing moves between the collapsed and the expanded configurations.
 17. A method for treating tissue, comprising: advancing a catheter of an ablation device through a body lumen to position a distal end of the catheter adjacent to tissue to be treated; retracting an actuator extending through the catheter to proximally retract an electrode coupled to a distal end of the actuator, wherein proximal movement of the electrode causes an expandable body to move from a collapsed configuration to an expanded configured; manipulating the catheter to position the electrode and the expandable body in contact with the tissue to be treated; actuating the ablation device to deliver energy to the electrode and to deliver fluid through at least one fluid pathway extending through the electrode, the fluid flowing through an expandable fluid channel at least partially defined by the expandable body.
 18. The method of claim 17, wherein retracting the actuator causes first and second tubes of the expandable fluid channel to slide relative to each other while maintaining the expandable fluid channel therethrough.
 19. The method of claim 17, wherein the expandable body includes a tube such that, when the expandable body moves from the collapsed configuration to the expanded configured, the tube expands radially outward in a direction perpendicular to a longitudinal axis of the catheter.
 20. The method of claim 17, wherein the expandable body covers a part of the electrode not in contact with the tissue during delivery of energy to the electrode.
 21. The method of claim 17, wherein the expandable body blocks energy from crossing an outer surface of the expandable body during delivery of energy to the electrode.
 22. The method of claim 17, further comprising releasing the actuator such that the expandable body reverts from the expanded configuration to the collapsed configuration, the expandable body being biased to the collapsed configuration. 